IPv4 vs IPv6: what's the difference?
The core difference is simple: IPv4 and IPv6 are two versions of the system that assigns addresses to devices on the internet. IPv4 is the older format with about 4.3 billion possible addresses, and IPv6 is the newer one built to supply a practically unlimited number.
What is IPv4?
IPv4 (Internet Protocol version 4) has been the internet's main addressing system since the early 1980s. Every IPv4 address is a 32-bit number, which people usually write in dotted-decimal notation: four numbers from 0 to 255, separated by dots, such as 203.0.113.7. That 32-bit design allows roughly 4.3 billion unique addresses.
Four billion sounds like a lot, but the internet outgrew it. Phones, laptops, servers, smart TVs, and countless other devices all need addresses, and the pool of available IPv4 addresses has effectively been exhausted. This scarcity is the main reason IPv6 was created. (For a broader primer, see what is an IP address.)
What is IPv6?
IPv6 (Internet Protocol version 6) is the successor designed to solve that shortage. Instead of 32 bits, each address uses 128 bits, which yields an address space so large it is effectively unlimited for any practical purpose. There are enough IPv6 addresses to give every device many times over, with room to spare for decades of growth.
Because 128-bit numbers are long, IPv6 addresses are written in hexadecimal rather than decimal. An address is split into eight groups of four hex digits, separated by colons, like 2001:0db8:0000:0000:0000:0000:0000:0001. To keep this readable, two shortening rules apply: leading zeros in a group can be dropped, and one run of consecutive all-zero groups can be replaced with a double colon (::). That same address becomes the much tidier 2001:db8::1. The :: can appear only once in an address, so there is no ambiguity about how many zero groups it stands for.
IPv4 vs IPv6 at a glance
Here is how the two compare on the points people ask about most:
- Address length: IPv4 is 32-bit; IPv6 is 128-bit.
- Format: IPv4 uses dotted decimal (
203.0.113.7); IPv6 uses colon-separated hexadecimal (2001:db8::1). - Address count: IPv4 offers about 4.3 billion addresses; IPv6 offers an astronomically larger number.
- NAT usage: IPv4 leans heavily on NAT (Network Address Translation) so many devices can share one public address; IPv6 has so many addresses that NAT is often unnecessary.
How IPv4 and IPv6 coexist today
The two versions do not talk to each other directly, so the internet did not simply switch from one to the other. Instead, most networks run both side by side in an arrangement called dual-stack. In a dual-stack setup, your device has both an IPv4 address and an IPv6 address, and it uses whichever one works best for the site you are visiting.
This is why sites, ISPs, and phone carriers support both. IPv4 is still dominant and reaches essentially every server on the internet, so it cannot be dropped. IPv6 adoption keeps growing because it relieves the address shortage and often provides a more direct connection. Supporting both means everyone stays reachable during this long, gradual transition.
Does a normal user need to care?
For everyday browsing, no. Your operating system, router, and ISP handle the choice between IPv4 and IPv6 automatically, and websites load the same either way. The distinction mostly matters if you run a server, host a game, configure firewall rules, or troubleshoot a network. Even then, the concepts above are usually all you need.
How to see which one you are using
The easiest way to check is to look at your own connection. You can see your IPv4 and IPv6 address right now: if a value appears in the IPv6 field, your connection supports it; if only an IPv4 address shows, your network is currently reaching the internet over IPv4. Many people find they have both, which confirms their setup is dual-stack.
The practical takeaway
IPv4 and IPv6 are two generations of the same idea, addressing devices on the internet, with IPv6 built to overcome IPv4's limited supply of addresses. IPv4 still carries most of today's traffic, IPv6 is steadily expanding, and running both together keeps the whole internet connected. As a user you rarely need to think about it, but knowing the difference makes it easy to understand what you are looking at when you check your own address.